Process and device for operating diaphragm metering pumps

ABSTRACT

Process and device for operating a diaphragm metering pump in which a charging pump is connected to a metering pump with a supply space for the transmitting liquid which is under atmospheric pressure and the pressure side is in communication with a space from which the pressure transmitting space is refilled.



1. A pump apparatus for metering a quantity of liquid, comprising: a supply chamber for containing the liquid under atmospheric pressure; a charging pump piston means for transferring liquid from said supply chamber to a pump chamber through a suction valve during its suction stroke; a pressure valve through which said piston means transfers liquid from said pump chamber to a refill chamber maintained under pressure and into a pressure transfer chamber during its pressure stroke; an unsupported diaphragm disposed at said pressure transfer chamber; and flow channels interconnecting said refill chamber, said pressure transfer chamber and said supply chamber whereby said transfer liquid may flow into said pressure transfer chamber after completion of the suction stroke at a pressure higher than atmospheric for shifting said diaphragm so as to meter said transfer liquid in a degassed condition by reason of said pressurized refill chamber while any excess pressure liquid may be returned to said supply chamber during the suction and pressure strokes of said piston means.
 2. The apparatus according to claim 1 wherein said piston means comprises a reciprocating pump piston and wherein a buffer piston is provided for varying the volume of said refill chamber thereby maintaining a constant pressure therein.
 3. The apparatus according to claim 2 wherein said buffer piston is spring loaded and wherein said refill chamber cooperates with an overflow bore leading to said supply chamber whereby said buffer piston may open said overflow bore after reaching a predetermined volume during the pressure stroke of said piston means. 